The present invention relates to a method for obtaining three-dimensional images of anatomical structures by reconstruction of two-dimensional X-Ray fluorograms.
X-ray imaging is widely used to image internal organs for diagnostic purposes and to assist health practitioners during therapeutic interventions. In particular, this technique has found many applications in cardiology. For example, many intraventricular interventional cardiac procedures such as Direct Myocardial Revascularization and electro physiological mapping and ablation are conducted under X-ray fluoroscopy.
X-ray fluorograms are two-dimensional projections of anatomical structures. While these images provide useful information they do not allow the resolution of the three-dimensional shape of these structures. Cardiologists typically overcome the deficiencies of the fluorograms by combining the 2-D information of X-ray fluorograms with their knowledge of anatomy to perform (therapeutics) cardiac procedures. This method has the disadvantage of relying heavily of the experience and knowledge of the practitioner.
Three-dimensional X-ray images of internal organs can be obtained using X-ray computed tomography. In this technique, a large number of projections is obtained from different angles and using image reconstruction techniques it is possible to reconstruct the image of an organ. This technique however requires long acquisition times and is not compatible with therapeutic interventions requiring xe2x80x9creal timexe2x80x9d information about the position of surgical instruments within an organ for example.
Bi-plane X-ray fluorograms can be used to determine the 3-D position of individual points such as the tip of a catheter. By obtaining several 3-D position of a catheter it is possible to produce a 3-D map of an organ such as a ventricle for example. However, this technique requires the use of an additional tool (the catheter) and furthermore the resulting map is not integrated with the fluorogram. Bi-plane fluorograms have also been used to derive 3-D images without the use of positional indicators as described in U.S. Pat. No. 4,672,651. This document describes an image reconstruction method based on a relaxative correction algorithm of projections-backprojections that requires extensive image processing.
The instant invention overcomes the limitations of the prior art by providing a method for rapidly reconstructing the three dimensional image of an object using a single plane two dimensional X-ray projection image.
In one aspect of this invention there is provided a method for reconstructing the three dimensional (3-D) image of an object, symmetric about at least one plane, from a single two dimensional (2-D) X-ray projection image.
According to one aspect of the present invention, there is provided a method of constructing a three dimensional image from a two-dimensional X-ray projection of an object. The method comprises steps of: a) filling the object to be imaged with an X-ray agent, the X-ray agent attenuating X-rays; b) generating an X-ray absorbance profile by irradiating the agent-filled object with X-rays substantially perpendicularly to a selected plane of the object, the object is substantially symmetrical about the selected plane thereof, wherein the X-ray absorbance profile has an x, y coordinates on the selected plane and has an absorbance parameter (P) related to a distance (D) travelled by the X-ray; and c) producing a three-dimensional image of the object using the X-ray absorbance profile, by dividing the X-ray absorbance parameter by two and processing the divided absorbance parameter into a z-coordinate with respect to the x, y coordinate of the corresponding absorbance profile.
According to another aspect of the present invention, there is provided a method of constructing a three dimensional image from a two-dimensional X-ray image of an object. The method comprises steps of: a) filling the object to be imaged with an X-ray agent, the X-ray agent attenuating X-rays; b) generating a two-dimensional X-ray image with respect to a selected plane of the object by irradiating the agent-filled object with X-rays substantially perpendicularly to the selected plane of the object, the object is substantially symmetrical about the selected plane of the object, wherein the two-dimensional X-ray image includes a plurality of picture elements, each picture element having an x, y coordinates on the selected plane and having an X-ray absorbance parameter (P) indicating a distance D(x, y) travelled by the X-ray; and c) producing a three-dimensional image of the object using the two-dimensional X-ray image, by dividing the X-ray absorbance parameter of each picture element by two and processing the divided absorbance parameter into a z-coordinate with respect to each corresponding picture element, thereby to generate x, y and z coordinates presenting a three-dimensional image of the object.
According to another aspect of the present invention, there is provided an apparatus for constructing a three dimensional image from a two-dimensional X-ray projection of an object. The apparatus comprises: a) means for filling the object to be imaged with an X-ray agent, the X-ray agent attenuating X-rays; b) means for generating an X-ray absorbance profile by irradiating the agent-filled object with X-rays substantially perpendicularly to a selected plane of the object, the object is substantially symmetrical about the selected plane thereof, wherein the X-ray absorbance profile has an x, y coordinates on the selected plane and has an absorbance parameter (P) related to a distance (D) travelled by the X-ray; and c) means for producing a three-dimensional image of the object using the X-ray absorbance profile, by dividing the X-ray absorbance parameter by two and processing the divided absorbance parameter into a z-coordinate with respect to the x, y coordinate of the corresponding absorbance profile.
The invention thus also relates to a method for the three dimensional image reconstruction of single plane 2-dimensional X-ray image projection of an object having at least one plane of symmetry comprising:irradiating said object with X-rays substantially perpendicular to said at least one plane of symmetry of the object; detecting said X-rays transmitted through said object to define a 2-dimensional projection mask image with pixels (x,y) having an intensity related to the absorbance of said object; substantially uniformly filling the object with an X-ray contrast agent said contrast agent having a pre-selected concentration and absorption coefficient; irradiating said contrast agent-filled object with X-rays substantially perpendicular to said at least one plane of symmetry of the object; detecting said X-rays transmitted through said contrast agent-filled object to define a 2-dimensional projection live image with pixels (x,y) having an intensity related to the absorbance of said contrast agent-filled object; subtracting said mask image from said live image to obtain a 2-dimensional final image; processing said 2-dimensional final image to reconstruct the 3-dimensional image of said object, said processing including determining a distance D(x,y) travelled by said X-rays in the contrast agent-filled object by dividing the absorbance corresponding to the intensity of each pixel (x,y) by the concentration of the contrast agent within said object and multiplying the result thus obtained by the absorption coefficient of said contrast agent; dividing said distance D(x,y) by 2 to define a (+z) coordinate (equals to +D(x,y)/2) and a (xe2x88x92z) coordinate (equals to xe2x88x92D(x,y)/2) for each pixel (x,y); such that for each pixel (x,y) there is:
1) a (+z) coordinate=+D(x,y)/2 and
2) a (xe2x88x92z) coordinate=xe2x88x92D(x,y)/2;
and using the x,y,z coordinates thus determined to reconstruct the 3-dimensional image in a 3-dimensional axis system in which the x-y plane is parallel to the plane of symmetry of said object.